Direct production of a lightCP-odd Higgs boson at the Tevatron and LHC

Abstract

We show that the existing CDF $L=630\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ Tevatron data on $pp\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}X$ places substantial limits on a light $CP$-odd Higgs boson $a$ with ${m}_{a}<2{m}_{B}$ produced via $gg\ensuremath{\rightarrow}a$, even for ${m}_{a}>2{m}_{\ensuremath{\tau}}$ for which $\mathrm{BR}(a\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})$ is relatively small. Extrapolation of this existing CDF analysis to $L=10\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ suggests that Tevatron limits on the $ab\overline{b}$ coupling strength in the region ${m}_{a}>8\text{ }\text{ }\mathrm{GeV}$ could be comparable to or better than limits from Upsilon decays in the ${m}_{a}<7\text{ }\text{ }\mathrm{GeV}$ region. We also give rough estimates of future prospects at the LHC, demonstrating that early running will substantially improve limits on a light $a$ (or perhaps discover a signal). In particular, outside the Upsilon peak region, integrated luminosity of only $5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}--20\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ (depending on ${m}_{a}$ and $\sqrt{s}$) could reveal a peak in ${M}_{{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}}$ and will certainly place important new limits on a light $a$. The importance of such limits in the context of next-to-minimal supersymmetric model Higgs discovery and $(g\ensuremath{-}2{)}_{\ensuremath{\mu}}$ are outlined.